This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Positive displacement motors (PDMs) are known in the art and are commonly used to drill wells in earth formations. Positive displacement motors traditionally have a power section, transmission section, and a bearing section in that order from the top connected to the drill string to the bottom connected to the drill bit. PDMs operate according to a reverse mechanical application of the Moineau principle wherein pressurized fluid is forced through a series of channels formed on a rotor and a stator in the power section. The channels are generally helical in shape and may extend the entire length of the rotor and stator. The passage of the pressurized fluid generally causes the rotor to rotate within the stator. The rotor is disposed through the stator and is connected to the drilling bit through a transmission shaft and a drive shaft to increase the rotational speed of the drill bit. The stator is connected with the drill collar which is connected to the drilling string. The drive shaft rotates at the higher speed of the drill bit and can suffer fatigue failures due to the high number of cycles it sees.
Turbine powered drill motors, known as turbodrills, utilize turbines to convert hydraulic power of the drilling fluid into mechanical rotation of an internal drive shaft which is connected to drill bit. The internal drive shaft rotates at a higher speed than the outer housing and the drill string.